1. Field of the Invention
Embodiments of the present invention generally relate to flat panel displays and particularly to compositions and methods for forming color filters for use in flat panel displays.
2. Description of the Related Art
Flat panel displays (FPDs) have become the favored display technology for computers, televisions, and personal electronic devices such as cell phones, personal digital assistants, etc. Liquid crystal displays (LCDs) are a preferred type of commercially available FPDs. Different colors are obtained in liquid crystal displays by transmitting light through a color filter located on a substrate of a LCD. The color filter includes pixels, wherein each pixel may include three colors, typically red, green, and blue. Each color of a pixel may be considered a sub-pixel. Typically, each sub-pixel is surrounded by a black matrix material that provides an opaque area between sub-pixels and therefore prevents light leakage in the thin film transistors (TFTs) of the LCD. FIG. 1 is a top view of two adjacent pixels 1 and 2 of a color filter 10. Pixel 1 includes three sub-pixels 3, 4, and 5, and pixel 2 includes three sub-pixels 6, 7, and 8. Black matrix material 9 surrounds and separates each of the sub-pixels 3, 4, 5, 6, 7, and 8. FIG. 2 is a side, cross-sectional view of color filter 10 showing substrate 12 upon which the black matrix material 9 and the pixels 1 and 2 (shown in FIG. 1) are formed. The sub-pixels 3, 4, and 5 are filled with three different colors of ink, 14, 16, and 18, respectively.
Traditional methods of producing color filters, such as dyeing, lithography, and electrodeposition, require the sequential introduction of the three colors. That is, a first set of pixels having one color is produced by a series of steps, whereupon the process must be repeated twice more to apply all three colors. The series of steps involved in this process includes at least one curing phase in which the deposited liquid color agent must be transformed into a solid, permanent form. Thus, such traditional methods of producing color filters can be very time consuming. Traditional color filter production methods also require expensive materials and typically have a low yield, which further increases the cost of producing color filters. Also, as each color agent is processed by a separate line of equipment, equipment costs for such traditional methods are high. In fact, the coast of manufacturing the color filter of a LCD may be as much as 20% of the total cost of manufacturing the LCD.
Methods of using inkjet systems that allow the deposition of all three colors simultaneously and that reduce the cost of manufacturing color filters have been developed. An inkjet system may be used to deposit different colors through different nozzles into sub-pixels created by a patterned black matrix on a substrate.
The development of inkjet systems for manufacturing color filters of LCDs has created a need for inks that can be dispensed by an inkjet without clogging the inkjet, i.e., have good jettability, and that do not degrade during inkjetting. In particular, there is a need for inks that are physically and chemically stable before, during, and after inkjetting and that have a color chromaticity that meets color filter specifications for both computer and television monitors, as well as for other devices containing displays.